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Does theoretical physics suggest that gravity is the exchange of gravitons or deformation/bending of spacetime?

What is the difference between gravitons and gravitational waves?Does quantum gravity entail that spacetime is emergent?Gravity and spacetime bendingWhat´s the physical foundation of the assumption that the curvature of spacetime can be quantised?Is the spacetime for gravity described with gravitons flat?Is the deformation of spacetime, elastic deformation or plastic deformation?Is gravity just the result of bending the space?Have the chances of finding gravitons changed now that we’ve detected gravitational waves?If gravity arises from the curvature of spacetime, why is there a need for gravitons?Does gravity CAUSE the bending of spacetime, or IS gravity the bending of spacetime?Does the existence of graviton contradict gravity being spacetime curvature?

14

5

$begingroup$

Throughout my life, I have always been taught that gravity is a simple force, however now I struggle to see that being strictly true.

Hence I wanted to ask what modern theoretical physics suggests about this: is gravity the exchange of the theoretical particle graviton or rather a 'bend' in space due to the presence of matter?

I don't need a concrete answer, but rather which side the modern physics and research is leaning to.

gravity spacetime curvature quantum-gravity carrier-particles

share|cite|improve this question

edited 20 mins ago

Kyle Kanos

21.6k114894

asked 19 hours ago

steve_just_stevesteve_just_steve

787

New contributor

steve_just_steve is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  I think that whichever model suits your need the best should get the job done. But then again I am not a Physicist.
  $endgroup$
  – harshit54
  18 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Well, even if you are not a physicist this is still a good point, so thank you.
  $endgroup$
  – steve_just_steve
  18 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @steve_jyst_steve: I was struggling to understand what was being asked here, so I took a moment to correct the grammar and phrasing. If you’re not happy with that, please just roll-back.
  $endgroup$
  – Mozibur Ullah
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @MoziburUllah Hello, and thank you very much for doing that, definitely sound better now!
  $endgroup$
  – steve_just_steve
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  An article in the New Yorker about looking at the same "thing" using different stances: A Different Kind of Theory of Everything (via Peter Woit's blog)
  $endgroup$
  – David Tonhofer
  13 hours ago
  

  
  
  
  

 | 
show 2 more comments

14

5

$begingroup$

Throughout my life, I have always been taught that gravity is a simple force, however now I struggle to see that being strictly true.

Hence I wanted to ask what modern theoretical physics suggests about this: is gravity the exchange of the theoretical particle graviton or rather a 'bend' in space due to the presence of matter?

I don't need a concrete answer, but rather which side the modern physics and research is leaning to.

gravity spacetime curvature quantum-gravity carrier-particles

share|cite|improve this question

edited 20 mins ago

Kyle Kanos

21.6k114894

asked 19 hours ago

steve_just_stevesteve_just_steve

787

New contributor

steve_just_steve is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  I think that whichever model suits your need the best should get the job done. But then again I am not a Physicist.
  $endgroup$
  – harshit54
  18 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Well, even if you are not a physicist this is still a good point, so thank you.
  $endgroup$
  – steve_just_steve
  18 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @steve_jyst_steve: I was struggling to understand what was being asked here, so I took a moment to correct the grammar and phrasing. If you’re not happy with that, please just roll-back.
  $endgroup$
  – Mozibur Ullah
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @MoziburUllah Hello, and thank you very much for doing that, definitely sound better now!
  $endgroup$
  – steve_just_steve
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  An article in the New Yorker about looking at the same "thing" using different stances: A Different Kind of Theory of Everything (via Peter Woit's blog)
  $endgroup$
  – David Tonhofer
  13 hours ago
  

  
  
  
  

 | 
show 2 more comments

$begingroup$

Throughout my life, I have always been taught that gravity is a simple force, however now I struggle to see that being strictly true.

Hence I wanted to ask what modern theoretical physics suggests about this: is gravity the exchange of the theoretical particle graviton or rather a 'bend' in space due to the presence of matter?

I don't need a concrete answer, but rather which side the modern physics and research is leaning to.

gravity spacetime curvature quantum-gravity carrier-particles

share|cite|improve this question

edited 20 mins ago

Kyle Kanos

21.6k114894

asked 19 hours ago

steve_just_stevesteve_just_steve

787

New contributor

steve_just_steve is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

share|cite|improve this question

edited 20 mins ago

Kyle Kanos

21.6k114894

asked 19 hours ago

steve_just_stevesteve_just_steve

787

New contributor

steve_just_steve is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|cite|improve this question

edited 20 mins ago

Kyle Kanos

21.6k114894

asked 19 hours ago

steve_just_stevesteve_just_steve

787

New contributor

steve_just_steve is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

edited 20 mins ago

Kyle Kanos

21.6k114894

edited 20 mins ago

Kyle Kanos

21.6k114894

asked 19 hours ago

steve_just_stevesteve_just_steve

787

New contributor

steve_just_steve is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 19 hours ago

steve_just_stevesteve_just_steve

787

2 Answers
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active

oldest

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25

$begingroup$

Both.

General relativity describes gravity as curvature of spacetime, and general relativity is an extremely successful theory. Its correct predictions about gravitational waves, as verified directly by LIGO, are especially severe tests.

Gravity also has to be quantum-mechanical, because all the other forces of nature are quantum-mechanical, and when you try to couple a classical (i.e., non-quantum-mechanical) system to a quantum-mechanical one, it doesn't work. See Carlip and Adelman for a discussion of this.

So we know that gravity has to be described both as curvature of spacetime and as the exchange of gravitons. That's not inherently a contradiction. We do similar things with the other forces. We just haven't been able to make it work for gravity.

Carlip, "Is Quantum Gravity Necessary?," http://arxiv.org/abs/0803.3456

Adelman, "The Necessity of Quantizing Gravity," http://arxiv.org/abs/1510.07195

share|cite|improve this answer

answered 16 hours ago

Ben CrowellBen Crowell

51.8k6158304

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hey man, the links you sent are very useful and this really helped clear up certain misconceptions I had about gravity, so it can and in fact is very likely to be both. Thank you very much :-) !!
  $endgroup$
  – steve_just_steve
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  This is probably a naive question, but wouldn't gravitons also produce gravitational waves, since the other forces do, e.g. EM waves?
  $endgroup$
  – gardenhead
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @gardenhead physics.stackexchange.com/questions/215173/… This suggests that gravitons are to gravitational waves as photons are to electromagnetic waves. So if my understanding is correct (don't bet on it, I mostly know classical physics), it is more like saying the graviton is the carrier on the quantum level for the gravatational waves.
  $endgroup$
  – JMac
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @JMac Your understanding is correct indeed.
  $endgroup$
  – Avantgarde
  11 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  " We do similar things with the other forces..." though it is clear what you mean (namely that force carriers particles naturally arise from gauge theories) this sentence is per sé slightly incorrect. The other forces live on a fixed (local) geometry at most coupling to it; they have the natural units to be (perturbatively) renormalisable - which is arguably not the case for the gravitational field (so in this respect it is indeed different from the pack).
  $endgroup$
  – gented
  10 hours ago
  
  
  

  
  
  
  

add a comment | 

5

$begingroup$

Gravity is as simple a force as all the others, which means that its simple when not looked at too closely, and far more sophisticated when it is. Given that it’s generally supposed all forces are merely low energy relics of a single high energy one, we might suppose that all the forces are as complicated as each other when looked at closely.

Popularly, Gravity is seen as different from the other forces in that its geometric. It turns out that the other forces are also geometric. Nevertheless, the main difference is that in gravity, the metric tensor, which tells us how to measure distances, times and angles is directly implicated in a way that it isn’t in the other forces. For example, there are two equations in EM, one of which does not involve the metric and hence seen as topological, and the other, which does (via the Hodge star) and hence, is coupled with gravity. The other two forces, the weak and strong force are modelled as gauge theories of the Yang-Mills type and hence directly generalising the EM equations. So similarly, they also have a topological and metric aspect, and the latter means it couples to gravity.

Now, whilst gravity hasn’t yet been quantised with several ongoing major projects that attempt this there are several partial semi-classical results which are used to help orientate research into this. One such result is that the quanta of gravity, the graviton, is a massless spin-2 particle. This is understood by looking at a linearisation of gravity which is used in the theory of gravitational radiation, and then by quantising this to show we have a massless spin-2 particle, aka the graviton.

share|cite|improve this answer

answered 14 hours ago

Mozibur UllahMozibur Ullah

4,98432252

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Thank you very much for your answer! Linearisation of gravity is definitely something to look into for me :-)!
  $endgroup$
  – steve_just_steve
  14 hours ago
  

  
  
  
  

add a comment | 

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25

$begingroup$

Both.

General relativity describes gravity as curvature of spacetime, and general relativity is an extremely successful theory. Its correct predictions about gravitational waves, as verified directly by LIGO, are especially severe tests.

Gravity also has to be quantum-mechanical, because all the other forces of nature are quantum-mechanical, and when you try to couple a classical (i.e., non-quantum-mechanical) system to a quantum-mechanical one, it doesn't work. See Carlip and Adelman for a discussion of this.

So we know that gravity has to be described both as curvature of spacetime and as the exchange of gravitons. That's not inherently a contradiction. We do similar things with the other forces. We just haven't been able to make it work for gravity.

Carlip, "Is Quantum Gravity Necessary?," http://arxiv.org/abs/0803.3456

Adelman, "The Necessity of Quantizing Gravity," http://arxiv.org/abs/1510.07195

share|cite|improve this answer

answered 16 hours ago

Ben CrowellBen Crowell

51.8k6158304

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hey man, the links you sent are very useful and this really helped clear up certain misconceptions I had about gravity, so it can and in fact is very likely to be both. Thank you very much :-) !!
  $endgroup$
  – steve_just_steve
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  This is probably a naive question, but wouldn't gravitons also produce gravitational waves, since the other forces do, e.g. EM waves?
  $endgroup$
  – gardenhead
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @gardenhead physics.stackexchange.com/questions/215173/… This suggests that gravitons are to gravitational waves as photons are to electromagnetic waves. So if my understanding is correct (don't bet on it, I mostly know classical physics), it is more like saying the graviton is the carrier on the quantum level for the gravatational waves.
  $endgroup$
  – JMac
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @JMac Your understanding is correct indeed.
  $endgroup$
  – Avantgarde
  11 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  " We do similar things with the other forces..." though it is clear what you mean (namely that force carriers particles naturally arise from gauge theories) this sentence is per sé slightly incorrect. The other forces live on a fixed (local) geometry at most coupling to it; they have the natural units to be (perturbatively) renormalisable - which is arguably not the case for the gravitational field (so in this respect it is indeed different from the pack).
  $endgroup$
  – gented
  10 hours ago
  
  
  

  
  
  
  

add a comment | 

25

$begingroup$

Both.

General relativity describes gravity as curvature of spacetime, and general relativity is an extremely successful theory. Its correct predictions about gravitational waves, as verified directly by LIGO, are especially severe tests.

Gravity also has to be quantum-mechanical, because all the other forces of nature are quantum-mechanical, and when you try to couple a classical (i.e., non-quantum-mechanical) system to a quantum-mechanical one, it doesn't work. See Carlip and Adelman for a discussion of this.

So we know that gravity has to be described both as curvature of spacetime and as the exchange of gravitons. That's not inherently a contradiction. We do similar things with the other forces. We just haven't been able to make it work for gravity.

Carlip, "Is Quantum Gravity Necessary?," http://arxiv.org/abs/0803.3456

Adelman, "The Necessity of Quantizing Gravity," http://arxiv.org/abs/1510.07195

share|cite|improve this answer

answered 16 hours ago

Ben CrowellBen Crowell

51.8k6158304

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hey man, the links you sent are very useful and this really helped clear up certain misconceptions I had about gravity, so it can and in fact is very likely to be both. Thank you very much :-) !!
  $endgroup$
  – steve_just_steve
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  This is probably a naive question, but wouldn't gravitons also produce gravitational waves, since the other forces do, e.g. EM waves?
  $endgroup$
  – gardenhead
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @gardenhead physics.stackexchange.com/questions/215173/… This suggests that gravitons are to gravitational waves as photons are to electromagnetic waves. So if my understanding is correct (don't bet on it, I mostly know classical physics), it is more like saying the graviton is the carrier on the quantum level for the gravatational waves.
  $endgroup$
  – JMac
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @JMac Your understanding is correct indeed.
  $endgroup$
  – Avantgarde
  11 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  " We do similar things with the other forces..." though it is clear what you mean (namely that force carriers particles naturally arise from gauge theories) this sentence is per sé slightly incorrect. The other forces live on a fixed (local) geometry at most coupling to it; they have the natural units to be (perturbatively) renormalisable - which is arguably not the case for the gravitational field (so in this respect it is indeed different from the pack).
  $endgroup$
  – gented
  10 hours ago
  
  
  

  
  
  
  

add a comment | 

$begingroup$

Both.

General relativity describes gravity as curvature of spacetime, and general relativity is an extremely successful theory. Its correct predictions about gravitational waves, as verified directly by LIGO, are especially severe tests.

Gravity also has to be quantum-mechanical, because all the other forces of nature are quantum-mechanical, and when you try to couple a classical (i.e., non-quantum-mechanical) system to a quantum-mechanical one, it doesn't work. See Carlip and Adelman for a discussion of this.

So we know that gravity has to be described both as curvature of spacetime and as the exchange of gravitons. That's not inherently a contradiction. We do similar things with the other forces. We just haven't been able to make it work for gravity.

Carlip, "Is Quantum Gravity Necessary?," http://arxiv.org/abs/0803.3456

Adelman, "The Necessity of Quantizing Gravity," http://arxiv.org/abs/1510.07195

share|cite|improve this answer

answered 16 hours ago

Ben CrowellBen Crowell

51.8k6158304

$endgroup$

share|cite|improve this answer

answered 16 hours ago

Ben CrowellBen Crowell

51.8k6158304

answered 16 hours ago

Ben CrowellBen Crowell

51.8k6158304

answered 16 hours ago

Ben CrowellBen Crowell

51.8k6158304

5

$begingroup$

Gravity is as simple a force as all the others, which means that its simple when not looked at too closely, and far more sophisticated when it is. Given that it’s generally supposed all forces are merely low energy relics of a single high energy one, we might suppose that all the forces are as complicated as each other when looked at closely.

Popularly, Gravity is seen as different from the other forces in that its geometric. It turns out that the other forces are also geometric. Nevertheless, the main difference is that in gravity, the metric tensor, which tells us how to measure distances, times and angles is directly implicated in a way that it isn’t in the other forces. For example, there are two equations in EM, one of which does not involve the metric and hence seen as topological, and the other, which does (via the Hodge star) and hence, is coupled with gravity. The other two forces, the weak and strong force are modelled as gauge theories of the Yang-Mills type and hence directly generalising the EM equations. So similarly, they also have a topological and metric aspect, and the latter means it couples to gravity.

Now, whilst gravity hasn’t yet been quantised with several ongoing major projects that attempt this there are several partial semi-classical results which are used to help orientate research into this. One such result is that the quanta of gravity, the graviton, is a massless spin-2 particle. This is understood by looking at a linearisation of gravity which is used in the theory of gravitational radiation, and then by quantising this to show we have a massless spin-2 particle, aka the graviton.

share|cite|improve this answer

answered 14 hours ago

Mozibur UllahMozibur Ullah

4,98432252

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Thank you very much for your answer! Linearisation of gravity is definitely something to look into for me :-)!
  $endgroup$
  – steve_just_steve
  14 hours ago
  

  
  
  
  

add a comment | 

5

$begingroup$

Gravity is as simple a force as all the others, which means that its simple when not looked at too closely, and far more sophisticated when it is. Given that it’s generally supposed all forces are merely low energy relics of a single high energy one, we might suppose that all the forces are as complicated as each other when looked at closely.

Popularly, Gravity is seen as different from the other forces in that its geometric. It turns out that the other forces are also geometric. Nevertheless, the main difference is that in gravity, the metric tensor, which tells us how to measure distances, times and angles is directly implicated in a way that it isn’t in the other forces. For example, there are two equations in EM, one of which does not involve the metric and hence seen as topological, and the other, which does (via the Hodge star) and hence, is coupled with gravity. The other two forces, the weak and strong force are modelled as gauge theories of the Yang-Mills type and hence directly generalising the EM equations. So similarly, they also have a topological and metric aspect, and the latter means it couples to gravity.

Now, whilst gravity hasn’t yet been quantised with several ongoing major projects that attempt this there are several partial semi-classical results which are used to help orientate research into this. One such result is that the quanta of gravity, the graviton, is a massless spin-2 particle. This is understood by looking at a linearisation of gravity which is used in the theory of gravitational radiation, and then by quantising this to show we have a massless spin-2 particle, aka the graviton.

share|cite|improve this answer

answered 14 hours ago

Mozibur UllahMozibur Ullah

4,98432252

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Thank you very much for your answer! Linearisation of gravity is definitely something to look into for me :-)!
  $endgroup$
  – steve_just_steve
  14 hours ago
  

  
  
  
  

add a comment | 

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Gravity is as simple a force as all the others, which means that its simple when not looked at too closely, and far more sophisticated when it is. Given that it’s generally supposed all forces are merely low energy relics of a single high energy one, we might suppose that all the forces are as complicated as each other when looked at closely.

Popularly, Gravity is seen as different from the other forces in that its geometric. It turns out that the other forces are also geometric. Nevertheless, the main difference is that in gravity, the metric tensor, which tells us how to measure distances, times and angles is directly implicated in a way that it isn’t in the other forces. For example, there are two equations in EM, one of which does not involve the metric and hence seen as topological, and the other, which does (via the Hodge star) and hence, is coupled with gravity. The other two forces, the weak and strong force are modelled as gauge theories of the Yang-Mills type and hence directly generalising the EM equations. So similarly, they also have a topological and metric aspect, and the latter means it couples to gravity.

Now, whilst gravity hasn’t yet been quantised with several ongoing major projects that attempt this there are several partial semi-classical results which are used to help orientate research into this. One such result is that the quanta of gravity, the graviton, is a massless spin-2 particle. This is understood by looking at a linearisation of gravity which is used in the theory of gravitational radiation, and then by quantising this to show we have a massless spin-2 particle, aka the graviton.

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answered 14 hours ago

Mozibur UllahMozibur Ullah

4,98432252

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share|cite|improve this answer

answered 14 hours ago

Mozibur UllahMozibur Ullah

4,98432252

answered 14 hours ago

Mozibur UllahMozibur Ullah

4,98432252

answered 14 hours ago

Mozibur UllahMozibur Ullah

4,98432252